1. Field of the Invention
The present invention also is directed to has as all object an alkaline battery provided with at least one bipolar electrode, in accordance with the invention also is directed to , and a manufacturing process for such an electrode.
2. Description of the Prior Art
It is well known that resorting to a bipolar pile all, that is to say, to a frontal collecting of the charging, has shown several advantages such as, in particular, the obtaining of a high mass energy when it deals with a high voltage battery (&gt;24 V). On the other hand, With respect to the alkaline batteries, such as the Ni-Cd, Ni-hydride, Ni-Zn, difficulties appear with such a method of assembly.
Basically, these difficulties are linked to the establishment of an electrical connection between the armature of the electrodes and the conductive screen separating the anode from the cathode; the assembly constitutes a bipolar electrode.
In patent FR 1711015 it is devised to solder the marginal portions of the electrodes (zones not filled with active materials) directly to the screen which, in many cases, is a metal strip. As a matter of fact, it was noted that the compatibility of the active material in the nickel sponges ensuring concomitantly the retention of the active materials and the collecting of the charges, cannot be effectuated after the soldering of the sponges to the strip because it leads to cracks in the strip and/or the tearing of the soldering spots.
In all instances, resorting to numerous soldering spots on the screen requires an extremely careful control of the soldering since any carelessness can bring about a perforation of the bipolar screen. Since the perforation of the screen would render the bipolar electrode unusable, it would result that such a method, although feasible, is very costly in view of the frequent adjustments and unavoidable waste.
Likewise, several patents, among which the German patent DE-A-29-07 262, submitted that the connection between the bipolar screen and the electrode or an intermediary conductive arrangement be merely carried out by pressure of the conductive zones of the electrode on the screen. Such a solution avoids any soldering but it was noted that, after a certain number of charging and discharging cycles of the element, it would lead to a progressive increase of the internal resistance of the battery, due to an increased value of the junction resistance between the metal structure of the electrode and the screen.
Furthermore, the realization of non-spillable, bipolar alkaline batteries implies that the design of the components be such, that the phenomena of recombination of the oxygen formed at the end of the charging could act with rapid kinetics. For this, in a bipolar electrode, such as the one described in patent DE-A-29 07 262, an intermediary tridimensional arrangement, such as a sponge or a sieve, is positioned between the active material of the electrodes and the bipolar screen.
Under these conditions, it is advisable to solve the aforementioned problems of connection at the level of the screen/intermediary arrangement and at the intermediary arrangement/armature of the electrodes.
On the other hand, resorting to the use of costly additional components, such as sponges and sieves, would entail significant costs.